This invention relates to a curable resin composition comprising a mixture and/or a preliminary reaction product of (a) a polyfunctional cyanate ester, a prepolymer of the cyanate ester or a coprepolymer of the cyanate ester and an amine (sometimes hereinunder referred to as component (a)), and (b) a polyisocyanate, a prepolymer of the polyisocyanate, or a coprepolymer of the polyisocyanate and an acid anhydride (sometimes hereinunder referred to as component (b)) and also relates to a curable resin composition comprising a mixture and/or a preliminary reaction product of component (a), component (b) and (c) a polyfunctional maleimide, a prepolymer of the maleimide or a coprepolymer of the maleimide and an amine (sometimes hereinunder referred to as component (c)). Cured resin obtained by curing each of the resin compositions has excellent mechanical property, heat-resistance and chemical resistance.
In the prior art, the cured resin obtained from a composition containing a polyisocyanate and an epoxy resin has low moisture resistance and storage stability.